Rotary pulverizer mill with flat face stator bars



Dec. 29, 1959 w, DOYLE 2,919,074

ROTARY PULVERIZER MILL WITH FLAT FACE STATOR BARS Filed Aug. 25, 1958 3 Sheets-Sheet 1 RECTANGULAR EAQ$ RECTAMGULAQ ATTORNEY W. T. DOYLE Dec. 29, 1959 ROTARY PULVERIZER MILL WITH FLAT FACE STATOR BARS 3 Sheets-Sheet 2 Filed Aug. 25, 1958 INVENTOR ATTORNEY Dec. 29, 1959 w. T. DOYLE 2,919,074

ROTARY PULVERIZER MILL WITH FLAT FACE STATOR BARS 3 Sheets-Sheet 3 Filed Aug. 25, 1958 INVENTOR ATTORNEY ROTARY PULVERIZlERMILL WITH FLAT FACE ST ATOR BARS.

William T. Doyle, Boston, Mass., assignor to Sturtevant Mill Company, Boston, Mass, a corporation of Massacliusetts Application August 25, 1958, Serial No. 756,852-

2' Claims. (Cl. 241-53) This invention relates to machines for grinding and classifying particles of material wherein the finely divided material is caused to be suspended in an air stream and, while in this suspended state, subjected to pulverizing forces. Thereafter, classified particles, in a desiredstate of subdivision, are carried off through a suitable discharge outlet.

For example, in pulverizing particles of the class represented by' insecticides, such as DDT, it may be desired to reduce particles from roughly A1. inch size down to screen sizes of 325 mesh or smaller. Furthermore, it is essential that material which has been pulverized is substantially free from any appreciable occurrence or To insuresuch an end undesirably coarse particles. result, it is necessary to subject all coarse particles to repeated grinding in order to prevent occasionally occurring coarse particles from escaping with the 325 mesh material. In thus subjecting the material to a repeated grinding a further problem arises in that some materials, particularly the DDT noted, tend to adhere to the inner periphery of the machine and form an undesirable layer of material which greatly detracts from the efliciency of the machine.

An object of the invention, therefore, is to improve pulverizing machines of the class indicated and deal with the problems indicated. Another object of the invention is to devise in a rotor type pulverizer machine, means for repeatedly subjecting particles to the action of rotor elements while, at the same time, developing an improved air classifying operation. Still another object is to devise a novel air classifier of the type having rotary blades with which there is combined a series of special particle guiding surfaces.

These and other objects and novel features will be more fully understood and appreciated from the following description of a preferred embodiment of the invention selected for purposes of illustration and shown in the accompanying drawings, in which Fig. 1 is a vertical cross sectional view taken centrally of the machine of the invention;

Fig. 2 is a plan cross section taken on the line 22 of Fig. 1;

Fig. 3 is a plan cross section taken on the line 3--3 of Fig. 1;

Fig. 4 is a cross section taken on the line 44. of

Fig. 1; and

Fig. 5 is a detail view showing a gate mechanismfor air control.

I find one successful means for realizing the foregoing objectives comprises a special rotor bar assembly with which is combined means for repeatedly displacing particles out of a helical path of travel in a novel manner. I have discovered that by causing particles to move in a helically directed stream which cuts across the paths of rotation of vertically spaced rows to rotary bars, it becomes possible to displace the particles slightly out of their normal helical path of travel in directions vertically upwardly and downwardly. Moreover, this effect can, I. find. be materially augmented. by interposing-z de Still further, I;

flector surfaces between the rotor bars. find: that by interrupting the. continuity ofv particle: retaining wall surfaces, displacement may bestill. further accomplished in directions radially inwardly with re. spect. to the paths of travel of the rotor bars. combined particle displacements result in greatlyincreasing the impact occurrence of the: bars with respect. to the particles of material and aihighly uniform grinding; operation is achieved. I

Considering in greater detail the combination of parts referred to, attention is directed to Fig. 1 in which is. mounteda casing 4. At a lower side ofthe. casing.-4.is.

a feed inlet 6 through which. particles ofv material are delivered by means of'ascrew conveyor 7' in a tubular conduit 8; A hopper 9 is arranged to receive the material and guideit onto the conveyor '7 to provide a desired:

rate of feeding.

In one typical instance ofa material handled andprocessed in the machine ofthe invention, there may be. citedan insecticide such as DDT which as noted earlier, may occur with a particle size of roughly 4 inch and which is required to bepulverized to a screen size of approximately 325 mesh. This 4 inch stock may be delivered, for example, at a rate of 1,200 pounds per hour or faster in a continuous operation. It will be understood that the specific materials, rates and. sizes-in..- dicated are not set forth in any limiting sense, but are.

merelyintended to be illustrative of any oneof a number. of similar operations.

At the. upper side of'the casing 4 is formed a discharge I outlet 10 through which pulverized material. may leave. the machine, as hereinafter described. Mounted for rotation about a vertical axis centrally of the casing. 4.

is a shaft 12 which has its lower end journalled .ina.

suitable bearing structure 14 supported, as shown in Fig.

1, in a bearing mount 16 on the base 2. A multiple. belt.

pulley 17 is fixed at the lower end of shaft 12 and isv arranged to be driven by suitable belts, as 18.

At the upper end of shaft 1 is supported a fan member 20 which is adapted to induce a helical stream of air to move upwardly through the casing and to be guided out of the discharge. outlet 10. The flow of air thus indnced is controlled by an. air control gate mechanism 22v best shown in Fig. 5 which opens or closes an air passage-- way 24. Air is drawn in through an opening 25 in the.

bottom ofv casing 4 and then passed through the passage- Way 24 when the fan is operating. The gate mechanism.

comprises a pair of plates 22a and 22 b which are supported in a bottom section 22c of the casing. and formed.

with some annular recessesadapted to fit around a sleeve portion 26 on shaft 12. Operating arms as. 28 extend outwardly in a position to be manually adjusted by an. operator.

In accordance with the invention, 1 combinewith the 7 various parts described above a special rotor bar arrangement, together withcooperating particle deflecting means. The rotor bar arrangement includes both rotary and stationary components. The rotary components comprise radially extending bars supported on a hub 30 as shown in Fig. 1 and occurring in vertically spaced. sets. Reference character R denotes rotor bars of any uppermost set, R" denotes rotor bars of a second set; and R" denotes rotor bars of a third set.

The three sets of rotor bars are rigidly held together by means'of interlocking pins as 34, 36, etc. as shown in Fig. 1. Extending into the spaces between the rotor bars R, R and R" are the stationary bar components which also occur in two sets including an upper set consisting of bars S and a lower set consisting of bars S. These stationary bars are supported through the sidewall of casing 4, and they are preferably constructed of sub- Patentedv Dec- 29, 1 959 The.

stantially rectangular or square cross sections so that they present flat deflecting surfaces. Particles carried upwardly in the air current described above strike against these surfaces and become deflected upwardly or downwardly into the paths of travel of adjacent rotating bars R, R, R". Consequently, all particles within fields of rotation of the bars undergo a greatly increased number of impacts with more grinding being accomplished. To deal with particles which are strongly acted on by centrifugal forces and which pass radially outwardly beyondthe bars I provide the additional deflecting means already referred to for deflecting particles radially inwardly so that they also are constrained to pass through the rotating bars. The additional deflecting means. are constructed as a part of a special casing liner member 40. This liner 40, when made of a relatively resilient rubber or rubber like material, I find, has the characteristics of resisting adhesion by firmly divided particles of a material such as DDT. Sticking or adhesion can be a very troublesome problem and is thus avoided. In this rubber liner 40, I also provide a plurality of vertically extending ribs as 40a, 40b, 40c and 40d, as shown in Fig. 4. These ribs project radially inwardly for a short distance sothat they tend to lie directly in the path of travel of particles moving in a helically ascending stream. As a result, particles at the outermost part of the stream are caused to strike against the ribs and to be thrown radially inwardly so that they again fall into the paths of travel of the rotating bars. In the rotor bar arrangement now described, it is possible with some types of relatively lighter materials for some particles to be drawn upwardly by the air and to pass around the rotor bar hub before they are subjected to suitable grinding action. 'Having in mind this possibiilty, I have further devised a novel air classifier arrangement for rejecting large particles. 'A principal component of this air classifier arrangement is a pair of revolving blades 50 and 52 which maybe fixed on shaft 12 as shown, or they may be removably secured so'that it is a simple matter to remove them if a lesser degree of classifying is desired. These blades act in the well-known manner to variably exclude travel of particles upwardly depending upon the speed at which they are rotated. In combination with these rotating blades, I provide conical deflector means 54 and 56 either one or both of which may be detachably secured and either used or removed as desired.

As shown in Fig. 1 these conical deflector members are chosen of a size such that they lie above and overhang slightly respective outer ends of the blades 50 and 52 with the result that some particles in'the outer helical stream are deflected downwardly and caused to be again subjected to grinding action of the rotor bars. Where both the conical deflectors 54 and 56 are employed, a repeated deflecting action takes place. It is pointed out that by means of the several deflector devices now described, a very large increase in the number of impacts occurs and this is sufficient to eliminate, for all practical purposes, the occurrence of occasional coarse particles in the machine output.

While I have shown and described a preferred embodiment of the invention, it should be understood that various changes and modifications may be resorted to within the scope of the appended claims.

I claim: a

1. A machine .of the class described, comprising a vertically disposed casing having a feed inlet'for introducing a material therein and a discharge outlet, a shaft mounted for rotation about a vertical axis centrally of the casing, fan means fixed to the shaft at its upper end for inducing a current of air to flow upwardly through the casing and moving particles of material in a helical path of travel toward the discharge outlet, vertically spaced sets of stationary bar elements extending radially inwardly from the casing and presenting flat deflecting surfacesfor displacing particles upwardly and downwardly rotor bar means fixed to the shaft at points above and below the stationary bars for pulverizing material enteringthefeed inlet classifier means supported in the casing above the rotor bar means for restricting particles of predetermined size from passing to the discharge outlet, an inner liner supported in the casing around the said rotor bar means said liner being formed with smooth cylindrical sections around which helically traveling particles may be slidably contained and said cylindrical sections being separated by vertically extending ribs which cooperate with the cylindrical sections of the liner to periodically displace particles out of their helical path of travel into the impact zone of the rotor bar means.

'2. A machine for pulverizing particles of material comprising a vertically disposed casing having a feed inlet for'introducing material particles therein and a discharge outlet for said particles, a shaft mounted for rotation about a vertical axis centrally of the casing, fan means fixed to the shaft at the upper end thereof and inducing a current of air to flow upwardly through the casing and move particles in an upwardly spiraling stream, said casing at its lower portion being formed H with an'air passageway for admitting air in responseto movement of the fan, valve means for opening and closing said air passageway, a plurality of radially extending rotor bars fixed to said shaft in the path of travel of particles entering the casing through said feed inlet, said rotor bars occurring in vertically spaced sets one above another, stationary interceptor bar means supported through the casing and projecting radially inwardly between the vertically spaced sets of rotor bars, said stationary interceptor bar means presenting fiat faces which.

are adapted to act on a stream of spirally directed air suspended particles induced by said fan and said rotor bars, and to cause the particles to be repeatedly displaced upwardly and downwardly into the respective paths of travel of said sets of rotor bars whereby impact grinding of the particles is carried out a resilient liner member extending around the casing and presenting sets of slide surfaces along which the helically traveling particles may move, and said slide surfaces being interrupted to present vertically extending ribs at spaced apart points therealong, said ribs constituting deflector means for periodically displacing particles moving around the slide surfaces into the path of the rotor bars to provide impact grinding in the absence of attritioninduced heating and sticking of the particles to the casing.

References Cited in the file of this patent UNITED STATES PATENTS 

